Fast acting switch utilizing a vaporizable wire



y 3, 1966 H. J. HUBER I 3,249,800

FAST ACTING SWITCH UTILIZING A VAPORIZABLE WIRE Filed Aug. 2, 1963 3 Sheets-Sheet 1 INVENTOR.

HENRY J. HUBER y 3, 1966 H. JLHUBER 3,249,800

FAST ACTING SWITCH UTILIZING A VAPORIZABLE WIRE.

Filed Aug. 2, 1963 .3 Sheets-Sheet 2 w cfyd u. EXPLODING WIRE CURRENT DWELL TIME V t HEATING PULSE# RESTR|KE b. SWITCH CURRENT INVENTOR.

HENRY J. HUBER BY m4. M

y 1966 H. J. HUBER 3,249,800

FAYST ACTING SWITCH UTILIZING A VAPORIZABLE WIRE Filed Aug. 2, 1965 3 Sheets-Sheet 3 0. CROWBARRED LOAD CURRENT b. UNCROWBARRED LOAD. CURRENT c. UNCROWBARRED LOAD VOLTAGE t SERIES SWITCH CLOSES 5 L CROWBAR SWITCH CLOSES United States Patent 3,249,800 FAST ACTING SWITCH UTHLIZING A VAPORIZABLE WIRE Henry J. Huber, Weehawken, N.J., assignor to the United States of America as represented by. the United States Atomic Energy Commission Filed Aug. 2, 1963, Ser. No. 299,677 9 Claims. (Cl. 315-111) This invention relates to fast-acting electrical switches and more particularly to a novel and improved fast-acting high energy switch of the explosion type. The invention described herein was made in the course of, or under, a contract with the United Atomic Energy Commission.

Many industrial and research apparatuses have required the operation of fast-acting switches for pulsing a circuit carrying electrical energy. In plasma research reactors, for example, fast-acting switches have been necessary at the correct time to pulse magnetic coils for the confinement of a plasma.

Conventional explosively actuated switches have been successfull in energizing circuits for such devices but these switches have been actuated by chemical burning or combustion of explosives which has been relatively unpredictable, slow-acting and dangerous. Also, these switches have had relatively high dynamic impedance or have not been rated for high voltages and currents. Also, the switches available heretofore have required relatively complicated, expensive or troublesome components or have had high wear rates. Additionally, it has been advantageous to provide a fast-acting, high energy, low impedance switch operable from a few percent to a high percent of the actuator breakdown voltage for either series or crowbar operation.

It has now been discovered, in accordance with this invention that a small metal wire can safely be exploded electrically and rapidly to pulse a circuit by electrically disintegrating the wire explosively to form a rapidly expanding current carrying low impedance conducting medium in the gap between two closely spaced conductors so as to actuate and conduct the flow of current between the conductors, while avoiding the heretofore known problems. More particularly, in one embodiment this invention provides a fast-acting switch for conducting large amounts of electrical energy, comprising first spaced electrodes forming a small gap, and means for providing a conductor in said gap between said electrodes, comprising an insulator between said first electrodes, a solid metal wire in said insulator, and fast-rising', pulsed, electrical energy source that disintegrates said wire explosively in the form of a rapidly expanding, current carrying, conducting medium which penetrates said insulator, is confined thereby, fills. the gap between said first electrodes, and conducts said electrical energy directly in a short path between said first conductors with low dynamic impedance.

The above and further novel features of this invention will appear more fully from the following detailed description when the same is read in connection with the accompanying drawings. It is to be be expressly understood, however, that the drawings are not intended as a definition of the invention but are for the purposes of illustration only. 7

In the drawings where like parts are marked alike:

FIG. 1 is a partial schematic drawing of the actuating means for the switch of this invention;

FIG. 2 is a partial cross-section of an embodiment of the switch to this invention;

FIG. 3 is a partial top view of the switch tnrough II-II;

FIG. 4 is partial schematic drawing of the delay time of the switch of FIG. 1;

FIG. 5 is a partial schematic drawing of the current of FIG. 1

3,249, 0 Patented May 3, 1966 and voltage vs. time characteristics of the apparatus of this invention;

FIG. 6 is a special top view of further apparatus for the switch of this invention.

Referring now to FIG. 1, the fast-acting low impedance, high rated switch 11 of this invention is shown as it is useful for rapidly pulsing a circuit for the confinement of plasma in a plasma research reactor. Plasma research reactors of the cusp confinement type having oppositely energized coils requiring a fast-acting, low impedance, high voltage, high current switch are disclosed, for example, in US. applications S.N. 746,309, filed July 2, 1958, by Friedrichs and Grad, now Patent 3,141,826, and US. Patents 3,038,099 and 3,031,398, which are all assigned to the assignee of this invention. It is understood, however, that the switch of this invention is useful in any other application where a fast-acting pulse is required and is particularly advantageous in pulse generators where is is necessary suddenly to switch on high voltages, with very low dynamic imepdance and where capacitors are required to be switched into a circuit at a small fraction of the peak capacitor voltage in a simple, inexpensive, safe and trouble-free manner.

Advantageously, leads 13 and 15 connect the opposite terminals of a standard energy source 17, such as a capacitor bank for energizing a load 19, such as standard magnetic cusp confinement coils, referred to above, which require opposite energization at high voltages and currents for confining a plasma. Suitable means (not shown) insuring low connection inductance, connect'leads 13 and 15 to switch terminals 20 and 21, and to this end these connections may be made by simply overlapping these conductors and applying a moderate pressure with appropriate fasteners that provide low connection resistance between the conductors. Advantageously, the electrodes 20 and 21 have a thin insulating film 22 bonded on their adjacent faces and the distance between the electrodes 20 and 21 is small, e.g., -0.025 inch (including film 22).

In accordance with this invention, an insulated, solid wire 23 is interposed between the closely spaced electrodes 20 and 21 and is electrically disintegrated explosively to penetrate the insulation and to form a rapidly expanding, current carrying, metallic conducting medium between the closely spaced electrodes 20 and 21 and to discharge the capacitor source 17 directly in a short path between the electrodes with low impedance. To this end the Wire is exploded electrically by a rapid rise time, electrical energy trigger pulser 24. Advantageously, this pulser comprises a switch 25 such as a spark gap having a first capacitor 27, and a suitable direct current source 29 for charging the capacitor 27. Also, an electrical second triggering source 31 having a switch 33, is provided which operates switch 25 so as to discharge capacitor 27 into wire 23 electrically to disintegrate wire 23 explosively in a very short time, -0.3 10 sec. or less. This explosion, in turn, penetrates the insulation around the wire and actuates the rapid discharge of the charge in capacitor bank 17 across terminals 20 and 21 to load 19 in an arc with very low impedance and at a fraction of the peak capacitor voltage, in a safe, simple and trouble-free manner. A new solid insulated exploding wire 23 may then be placed between electrodes 20 and 21 and the depression of switch 37 charges capacitor 17v from a suitable source 39. This capacitor is then discharged to load 19 by depressing switch 33 which causes switch 25 rapidly to discharge into and through this new solid wire 23 to penetrate its insulation, to explode the wire and to discharge capacitor bank 17 consistently in a very short time, in a very short path across electrodes 20 and 21, and in a thick or low impedance arc with a relatively large area of contact on inserts 41 and 43.

Referring now to FIG. 2, in one embodiment, parallel upper and lower electrodes 20 and 21 have suitable low sputtering tungsten cylindrical inserts 41 and 43 facing each other to form shallow opposite recesses 45 and 47 or reaction chambers co-extending with a gap 48 between inserts 41 and 43 when switch 11 is fired. Stainless steel inserts may also be used, with slightly less insert life and deeper recess spacing. One of these inserts, such as insert 43, has a hole 49 which vents the high pressure gases produced by discharge of capacitor 17 in gap 48 through a corresponding hole 51 in electrode21. Tie bolts 53 and 55 pass through insulators 57 and electrode 20 adjacent one end of the bolts and thread into electrode 21 adjacent the other end of the bolts to hold the electrodes in close spacing across a space 59 and to dispose the exploding solid wire 23 therebetween in gap 48.

Advantageously, exploding solid wire 23 is imbedded between two laminated, parallel sheets (61 and 63 as shown in FIG. 3) of a tough dielectric, such as polyethylene coated mylar, which form a closed insulator 65, or case around wire 23 about .006 inch thick. The electrodes 20 and 21 compress across insulator 65 in the space between the electrodes. This space 59 surrounds the sides of gap 48 and reaction chambers 45 and 47 on the opposite sides of insulator 65 in gap 48. These small spaces in gap 48, which are formed by recesses 45 and 47, prevent the solid wire 23 from being compressed in gap 48 to cause the misfiring thereof.

Solid wire 23, which is advantageously only a 0.001 inch diameter aluminum wire, is connected through wide conductors with its rapid rise time, electric pulse from trigger pulse 24 for exploding solid wire 23. To this end the wire 23 is disposed between and bridges wide foil strips 67 and 69 connected to capacitor 27. In actual practice wire 23 bridges the foil strips without soldered connections, and the foils are 0.001 inch thick, one-half inch Wide and spaced 0.2 inch apart. The foils, however, may be wider, closer or farther apart. Also, these foil strips connect with leads 71 and 73, which make a circuit with the opposite ends of capacitor 27. These leads 71 and 73 have pointed ends (one end 75 of which is shown in FIG. 2) which insulator 77 holds fixed in electrode '21 so as to puncture the ends 79 of the foil strips and thereby to make contact with the foil strips, as shown in FIG. 3, when tie bolts 53 and 55 clamp electrodes 20 and 21 together against insulator 65.

In operation, the depression of switch 3-7 charges capacitor bank 17 from source 39. Thereafter, depression of switch 33 causes source 31 to trigger spark gap 25 and this rapidly discharges the energy in capacitor 27 through leads 71 and 73 to disintegrate solid wire 23 explosively in gap 48 in the form of a rapidly expanding current-carrying, conducting medium which penetrates sheets 61 and 63 of insulator 65. This penetration of insulator 65 communicates the opposite sides of gap 48 through insulator 65, i.e., connects the reaction chambers formed by recesses 45 and 47, confines the exploded wire in the hole produced in insulator 65 and fills the gap 48 with vaporized wire. This vaporized wire 23 provides an instantaneous discharge are between inserts 41 and 43 and rapidly and completely discharges the low or high charge in capacitor 17 from electrode 20 to electrode 21 through inserts 41 and 43 in the shortest path between these inserts and with a low dynamic impedance. In actual tests pulses have been switched with voltages of up to 20 kv. and currents of 200 ka., with a dynamic inductance of less than 2X10- henries and a crow-bar resistance of less than X10 ohms.

These low inductance and resistance values indicate that no problem was encountered with'the switch of this in-v vention by a high, magnetic pressure, pinch effect SLlfl'lClGlll'. to squeeze the current channel between inserts 41 and 43 to a very thin thread having a high resistance and inductance. Undoubtedly a pinch effect can be produced, but it is'not a severe problem even when the switch of FIG. 2 switches currents as high as 2x10 amps in a single are. This was done by directly shorting a 24 kilocycle 20 kv. capacitor bank. Also, exploding solid wire 23 distributes the main discharge current over a large area of inserts 41 and 43 in the reaction chambers or recesses 45 and 47 so that the high forces produced by small diameter high current arcs has not been a problem. Additionally, the distance between inserts 41 and 43 is small and the distance traveled by the current between inserts 41 and 43 is also small whereas a wide spacing or long current path would produce high impedance to the fiow of this current, increase the actuation time of switch 11, and decrease the current discharged from capacitor 17.

To provide repeated switching in a cycle, the upper electrode 20 lifts up and a disposable actuator 81 comprising a wire 23, foil strips 67 and 69 and insulator 65, is placed in position between electrode 20 and 21. Tie bolts 53 and 55 then clamp up the components of switch 11 whereby the sharp ends of foil leads 71 and 73 automatically pierce through rnylar laminated insulator 65 to the foil strips 67 and 69 thus to connect the trigger pulser-24 to the bridge wire 23. 7

At a pre-set time, depending on when switching must occur, the spark gap in the trigger pulser is rapidly triggered thus rapidly discharging its capacitor 27 into solid bridge wire 23, the respective wires 23 exploding consistently and in a very short time (-0.3 10" sec.) to rupture the insulator 65 and to fill the gap 48 between the electrodes 20 and 21 with a metal conductor and an arc with low impedance. The switch 11 now being in its conducting state, it should be noted that the small recesses 45 and 47 (each 0.010 inch deep) prevent the wire being restricted by compression produced by tie bolts 53 and 55, since such restriction can prevent the proper explosion of the wire 23 and thereby cause a malfunction of the switch 11. Once the switch is actuated, it will not stop conducting until the energy in the external circuit is dissipated.

The switch is then opened by loosening the tie bolts 53 and 55 to complete this cycle of operation and for the replacement of the used actuator 81 with another actuator for the next cycle.

The insertion of actuators 81 having explodable wires 23 therein may be by hand operation or by automatic operation. To this end these actuators may be disposed in a continuous strip and fed through switch 11 from a first supply spool to a second take-up spool. Continuous strip action is desirable, particularly for automatic operation. To this end four tie bolts can be used which allow such a strip to travel between them. These spools may be suitably driven either by hand or automatically by a gear train having electric motors like motors 85 and 87 (FIG. 6) which feed the continuous actuator strip into switch 11 when open and to the proper position by means of suitable limiting switches which stop the motors and actuator strip in this proper position for re-clamping.

In making the actuators 81 for commercial operation, thin metal foil has been applied to a thin sheet of mylar dielectric with heat and pressure. A mask, such as wax, has then been applied to the foil and a portion of the mask has been removed for etching. This etching, with an acid, has then removed all the unmasked metal foil in a pattern to leave parallel foil strips bridged by a thin metal wire. Thereupon another mylar sheet has been laminated under heat and pressure against the remaining foil and thin wire to provide the necessary exploding Wire actuator. This simple process allows the actuators to be made in continuous lengths and in high volume with low cost and accurate wires 23.

The maximum allowable trigger voltage is determined first by choosing the conditions under which the switch 11 operates and then using disposable actuators 81 with bridge wires 23 omitted and measuring the trigger 24 voltage which causes a puncture in the insulator 65. Using a trigger pulse slightly below this value will insure breakdown in the insulator due to wire 23 explosion.

The current in solid exploding wire 23 can be broken down into two parts, as shown in FIG. 4, comprising a heating pulse and a restrike. Under most conditions conduction between the main electrodes 20 and 21 starts shortly after the restrike begins. The dwell time (interval between the end of the heating pulse and the beginning of the restrike) depends on parameters such as pulser voltage, pulser capacitance, bridge wire 23 length, bridge Wire material, and the ambient pressure around the bridge wire. In all cases, however, the restrike can be accurately timed and is concurrent with an instantaneous current carrying arc between electrodes 20 and 21.

Typical values in an actual switch 11, according to this invention, are illustrated by the following actual parameters and characteristics which have been provided:

Main capacitor bank 17 voltage -20 kv. Peak load 19 current 100200 ka. Bank 17 capacitance 6,.LF.

Self resonant frequency 250 kc./s. Load coil 19 inductance 10- h. Peak crowbarred current 100-200 ka. Inherent crowbar delay 0.3 x 10- sec.

(Time interval from start of current in bridge wire 23 to conduction across main electrodes 20 and 21) Measured crowbar inductance 2 10 h. Measured crowbar resistance 5 X 10- Trigger pulser 24 supply voltage 3 kv.

Trigger pulser 24 capacitance 2.0 F. Frequency of exploding wire 23 current- 125 kc./s. Peak exploding wire 23 current -5 ka. Exploding Wire 23 length 0.2 in. Exploding wire 23 material 0.001 in. alum.

In this an actual illustration of the switch of FIG. II, currents as high as 2x10 amps at 20 kv. have been switched. The energy discharged and self resonant fre quency were 24 kilojoules and 150 kc./s. Measured inductance was about 3 1() h.

The bridge wire 23 pulse consumes only a small portion of the capacitor voltage coming from trigger 24. The remaining voltage on the capacitor can only cause restrike if the heated wire, now a dense vapor, is allowed to expand. Recesses 45 and 47, and vent holes 49 and 51 are provided to vent the violent discharge, between the main electrodes 20 and 21. Also, recesses 45 and 47 prevent the sputtered electrodes from piercing actuator 81 and thus causing a premature breakdown of the switch.

Since the switch of this invention has very low dynamic impedance an can operate over a broad range of voltages from a few percent to about 90% of the actuator static breakdown voltage it can be used for either series or crowbar switching. If only the series switch is fired, the current waveform corresponds to FIG. 5b. If the crowbar switch is fired at time t i.e., the first maximum of load current, then the current waveform corresponds to FIG. 5a. If both switching modes are used, damped oscillations will be eliminated.

In series switch operation of switch 11 series operated actuator strips 81 are provided with the above-described wires 23 disposed therein. These wires 23 are then placed in series operated gaps 48 and triggered by trigger'24 to discharge capacitor bank 17 across the gaps 43 through conductors 20 and 21 forming the gaps.

Tests on a series operated 0.003 inch thick mylar laminated actuator 81 indicated a constant delay of only about 0.3 10 seconds for a range of voltages of 500 v. to 4 kv. at a frequency of 45 kc./s. Using a 600 kc./s. exploding wire pulser and a 0.006 inch thick laminated actuator at 10 kv., a 120 ka. pulse was also switched at 300 kc./s. Here, a reduction of the trigger pulser capacitance from 2 [.LF. to 0.5 ,uF. also improves switch timing because of the.higher frequency of exploding wire current.

The principles of the exploding solid wire 23 of this invention can easily be extended to even high voltages and currents than mentioned above. To this end the parallel use of more than one wire 23 increases the energy capacity and reduces the switch inductance. For maximum energies and currents (e.g. 100K joules and several million amperes) parallel operated wires 23 may be in contact with a thin continuous layer of small amounts of high explosive PETN powder applied in a thin coat 101 around wire 23 and ignited by the exploding wire 23. The pressure shock of the explosive partially compensates the magnetic pressure coming from the pinch effect in the magnetic field surrounding the discharge between electrodes 20 and 21 since this effect can squeeze the current channel of this discharge into a very thin thread and increase the resistance and inductance at these higher values. Such an explosive coating is shown, for example, in FIG. 6 as it is applied on each individual wire 23 in a continuous strip 81 with the ends of leads '71 and 73 in a line. Motors 85 and S7 fed this strip 81 into switch 11.

Unlike other switches, switch 11 is not dependent on polarity across the main electrodes. This invention also provides an inexpensive, fast acting switch for switching high energy pulses. For example on a 5000 actuator basis for a lK-joule, 25 kv., 250 ka. switch, the cost of each actuator is about 50 cents or less. This invention also has the advantage of providing a simple, safe and trouble free switch, operable rapidly to switch pulses with low dynamic impedance, and to crowbar capacitors at a small fraction of the peak capacitor voltage. Also, the thin exploding wire of this invention is easily fabricated without soldered connections, is automatically fed and connected for switching between two very closely spaced electrodes and is exploded without damage to the switch and with minimal wear to the switch parts. Actual tests, for example, have shown this invention to be operable as described for at least 50 shots without replacement of the inserts 41 and 43. Additionally, a low voltage, low energy trigger pulse is operable therewith in crowbar or series operation and the heretofore known dangerous or unpredictable switch actuation by high explosives is avoided.

What is claimed is:

1. A fast acting electric switch for conducting large amounts of electrical energy, comprising first closely spaced electrodes forming a small gap, and means for providing a metal conductor in said gap which connects said first electrodes, comprising a flat insulator having an unrestrictive portion between said first electrodes forming small, reaction chambers therewith spaced metallic foils in said insulator having therebetween, an aluminum wire in said unrestricted portion of said insulator, a capacitor having an electrical energy source for selectively charging said capacitor, and a spark gap having a trigger for sparking said spark gap to connect said capacitor suddenly with said metallic means across said spark gap, said wire having a thin cross-section in said insulator between said first electrodes which electrically heats and explodes int-o said chambers in the form of a dense, rapidly expanding, current carrying, conducting metal which penetrates said insulator, forms a hole therein, is.

confined thereby suddenly to fill said reaction chambers between said first electrodes with a thick arc and which suddenly conducts large amounts of electrical energy between said first electrodes with low dynamic impedance, whereby said metal is capable of high pulse voltages between said first electrodes, and an ability to switch said large electrical energy conduction at a small fraction of its peak pulse voltage when said electrical energy source and said metallic means are connected thereby.

2. The invention of claim 1 in which said peak exploding wire current is about 5 ka., and said wire explodes in about O.3 10- sec. to form the dense conducting medium.

3. The invention of claim 1 in which said first electrodes are spaced about 0.025 inch apart, and the dis charge between said electrodes has an inductance less than 2x10 henry and a resistance less than 10 ohms.

4. A method for forming an explodable metallic conductor, comprising applying a wide aluminum foil to an insulator, applying a mask to said foil, removing a portion of said mask for etching a portion of said foil, etching said portion of said foil to produce a thin crosssectional area thereof, and applying a layer of insulation to said etched foil.

5. A fast acting electric switch for conducing electrical energy in a first circuit, comprising spaced, parallel, first and second flat sided electrodes forming a gap in said first circuit between said electrodes and cylindrical recesses on opposite sides of said gap, cylindrical metallic inserts in said recesses separated from each other across said gap a distance greater than the width of said gap to form opposite adjacent reaction chambers in said electrodes between said inserts, one of said inserts and electrodes forming a venting hole communicating with the respective reaction chamber formed by said one of said inserts and electrodes, a continuous, fiat sided insulator in said gap between said electrodes containing spaced foils having a thin connecting wire between said foils in a second circuit in said insulator adjacent said reaction chambers, and means for energizing said foils with a fast, electrical energy pulse explosively to vaporize said wire in the form of a rapidly expanding, current carrying, conducting medium in said gap between said inserts directly to conduct said energy in a short path across said gap between said inserts in said first circuit and to break the second circuit through said foils.

6. The invention of claim 1 in which said Wire is a 0.2 inch long aluminum wire having a .001 inch diameter.

7. A fast acting electric switch for conducting electrical energy in a first circuit, comprising spaced parallel first and second fiat sided electrodes forming a gap in said first circuit between said electrodes and cylindrical recesses on opposite sides of said gap, cylindrical metallic inserts in said recesses separated from each other across said gap a distance greater than the width of said gap between said electrodes to form opposite adjacent reaction chambers in said electrodes between said inserts, one of said electrodes and inserts forming a venting hole communicating with the respective reaction chamber formed by said one of said electrodes and inserts, a continuous flat sided insulator in said gap between said electrodes containing spaced foils having a thin conducting wire between said foils in a second circuit in said insulator adjacent said reaction chambers, pointed conducting means in at least one of said electrodes and insulated therefrom, means for selectively moving said electrodes relatively oppositely to decrease the width of said gap for causing said pointed conducting means to pene trate said flat-sided insulator to make electrical contact with said foils, and means for energizing said pointed conducting means with a fast, electrical energy pulse electrically to heat and vaporize said thin wire explosively in the form of a rapidly expanding, electrical current carrying, conducting medium that penetrates said insulator and fills said reaction chambers to conduct said electrical energy directly in a short path between said inserts in said circuit with low impedance.

8. A fast acting electric switch for conducting electrical energy in a first circuit, comprising spaced, parallel, first and second flat sided electrodes forming a gap in said first circuit between said electrodes and cylindrical recesses on opposite sides of said gap, cylindrical tungsten inserts in said recesses separated from each other. across said gap a distance greater than the width of said gap between said electrodes to form opposite adjacent reaction chambers in 'said electrodes between said inserts, one of said electrodes and inserts forming a venting hole communicating with the respective reaction chamber formed by said one of said electrodes and inserts, a continuous flat sided insulator in said gap between said electrodes containing a plurality of pairs of spaced foils having a thin conducting wire between each of said pairs of spaced foils in a second circuit in said insulator, pointed conducting means in at least one of said electrodes and insulated therefrom, means for selectively moving said electrodes relatively oppositely to decrease the width of said gap for causing said pointed conducting means to penetrate said flat-sided insulator to make electrical contact with said foils, said means for selectively moving said electrodes also moving said electrodes to increase the width of said gap for locating each of said wires sequentially adjacent said reaction chambers, and means for energizing said pointed conducting means with a fast,.

9. The invention of claim 8 having means for moving I said continuous flat, insulating means longitudinally between said electrodes selectively, sequentially to position respective of said wires adjacent said reaction chambers for exploding said wires for repeatedly discharging said electrical energy between said inserts in said first circuit.

References Cited by the Examiner UNITED STATES PATENTS 2,400,408 5/ 1946 Haefelfinger 2001 18 2,964,436 12/1960 Mikulis et al 29155 3,070,873 1/ 1963 Gordon et a1 29155 3,083,443 4/1963 Hergenrother 29-155 3,102,936 9/1963 Swift 200118 3,104,295 9/ 1963 Bender 200-87 3,157,120 11/1964 Morgan 313-231 IPAVID J. GALVIN, Primary Examiner.

BERNARD A. GILHEANY, GEORGE N. WESTBY,

Examiners.

H. B. GILSON, S. D. SCHLOSSER, Assistant Examiners. 

1. A FAST ACTING ELECTRIC SWITCH FOR CONDUCTING LARGE AMOUNTS OF ELECTRICAL ENERGY, COMPRISING FIRST CLOSELY SPACED ELECTRODES FORMING A SMALL GAP, AND MEANS FOR PROVIDING A METAL CONDUCTOR IN SAID GAP WHICH CONNECTS SAID FIRST ELECTRODES, COMPRISING A FLAT INSULATOR HAVING AN UNRESTRICTIVE PORTION BETWEEN SAID FIRST ELECTRODES FORMING SMALL, REACTION CHAMBERS THEREWITH SPACED METALLIC FOILS IN SAID INSULATOR HAVING THEREBETWEEN, AND ALUMINUM WIRE IN SAID UNRESTRICTED PORTION OF SAID INSULATOR, A CAPACITOR HAVING AN ELECTRICAL ENERGY SOURCE FOR SELECTIVELY CHARGING SAID CAPACITOR, AND A SPARK GAP HAVING A TRIGGER FOR SPARKING SAID SPARK GAP TO CONNECT SAID CAPACITOR SUDDENLY WITH SAID METALLIC MEANS ACROSS SAID SPARK GAP, SAID WIRE HAVING A THIN CROSS-SECTION IN SAID INSULATOR BETWEEN SAID FIRST ELECTRODES WITH ELECTRICALLY HEATS AND EXPLODES INTO SAID CHAMBERS IN THE FORM OF A DENSE, RAPIDLY EXPANDING, CURRENT CARRYING, CONDUCTING METAL WHICH PENETRATES SAID INSULATOR, FORMS A HOLE THEREIN, IS CONFINED THEREBY SUDDENLY TO FILL SAID REACTION CHAMBERS BETWEEN SAID FIRST ELECTRODES WITH A THICK ARC AND WHICH 